The Office of Inspector General’s (OIG) Office of Evaluation and Special Projects is examining the State Department’s records preservation and the use of personal hardware and software by five Secretaries of State (Albright, Powell, Rice, Clinton, and Kerry) and their immediate staff. On March 4, State/OIG posted the OIG (Linick) – M (Kennedy) memorandum on classified material discovered in the archives and its removal for secured storage:

During the course of this evaluation, OIG searched unclassified archives and discovered records suggesting instances in which potentially sensitive material may have been transmitted via personal email accounts or other unclassified means to Secretary Powell or to Secretary Rice’s immediate staff. None of the material was marked as classified, but the substance of the material and “NODIS” (No Distribution) references in the body or subject lines of some of the documents suggested that the documents could be potentially sensitive. On October 19, 2015, OIG transmitted to the Department and separately to the Inspector General for the Intelligence Community (ICIG) for classification review 19 separate Office of the Secretary archival documents. The date range of the documents is from February 2003 through June 2008.
[…]
On December 29, 2015, the Department advised OIG that 12 of the 19 documents contain national security information classified at the Secret or Confidential levels based on a review by 9 Department bureaus and offices. Two of these documents were emails sent to Secretary Powell’s personal email account; the remaining were documents transmitted to personal or unclassified accounts belonging to a member of Secretary Rice’s immediate staff and another senior Department official.
[…]
State’s official response: Office of the Executive Secretariat (S/ES) staff have removed from the Department’s unclassified network all of the email material identified as classified and placed it in secure storage. Additionally, retired electronic records provided to the Bureau of Administration that were initially stored in an unclassified system have b~enmoved to the appropriate classified system. With regard to paper records relating to former Secretaries Powell and Rice, the Department does not believe any action is warranted because these materials are currently stored in a facility certified to house classified Department record~up to the SECRET level.